A study by Krishna et al. (2015) reported that the inability of the CD4+CD25+ T cells, extracted from the entire peripheral blood mononuclear cell population, to expand during the follicular phase is most likely a consequence of an inherent hyporesponsiveness to IL2 signaling and compromised STAT5 activation in women with PCOS [32]. This evidence concerns the gene CD4 and polycystic ovary syndrome.